Broadband, multichannel signal distribution systems provide secure channel signal allocation to selected subscribers. In the past, security of the channel information has been provided by two methods, either passive trapping or removal of the channel information, or signal jamming or obscuring the channel information with a secondary signal to make the channel information unusable In passive trapping, an electronic band-stop filter is installed in the customer's connection (drop) to eliminate those signals which the customer is not authorized to receive. The passive trap is typically installed at the drop, and may be actuated at the drop either manually or electronically by a control signal from a remote control point. However, signal traps are subject to frequency drift under changing temperature, and the temperature drift causes the signal trap to drift from the carrier frequency, thus allowing unauthorized customer access to the channel. Moreover, as signal traps tend to be quite wide in bandwidth at higher frequencies, the use of such filters is made economically unfeasible or, alternately, makes the adjacent channels also unusable.
Signal jamming typically provides a narrow band continuous 10 wave (CW) carrier or modulated carrier which is added to the signal channel of interest. To recover the signal, the authorized customer is given a narrow band trap to remove the jamming signal. However, the trap used to remove the jamming is also subject to temperature drift. When the drift occurs, a recovered signal could become unusable or marginally usable. Moreover, the trap may remove not only the jamming carrier but also some of the desired signal, thus degrading the quality of the received signal. Furthermore, since a trap of this nature is installed at the customer location, a customer having electronic knowledge can easily design a device to remove the jamming signal and thus recover the desired signal without authorization.